四川马边铜厂埂磷矿床稀土元素地球化学特征  

REE GEOCHEMICAL CHARACTERISTICS OF TONGCHANGGENG PHOSPHATE DEPOSIT IN MABIAN COUNTY,SICHUAN PROVINCE

作　　者：张玙[1] 程文斌[2] 杨豫川 王畅 曾敏[2] 金灿海[1] 董树义[2] Zhang Yu;Cheng Wenbin;Yang Yuchuan;Wang Chang;Zeng Min;Jin Canhai;Dong Shuyi(Chengdu Center of China Geological Survey,Chengdu,Sichuan,610081,China;College of Earth Science,Chemgdu University of Technology,Chengdu,Sichuan 610059,China;No.207 Geological Team,BGEEMRSP,Leshan,Sichuan 614000,China)

机构地区：[1]中国地质调查局成都地质调查中心,四川成都610081 [2]成都理工大学地球科学学院,四川成都610059 [3]四川省地质矿产勘查开发局二零七地质队,四川乐山614000

出　　处：《矿物岩石》2020年第1期50-59,共10页Mineralogy and Petrology

基　　金：中国地质调查局地质调查项目(DD20160019,DD20160019-06,DD20160019-16,121201010000150002-11)。

摘　　要：铜厂埂磷矿床赋存于下寒武统麦地坪组地层中,是川滇磷矿带中典型的沉积型磷矿床,针对该矿床的稀土元素地球化学研究,旨在揭示其沉积环境的演变。研究表明,铜厂埂磷矿床中测试样品的ΣREE介于26.13~172.42×10^-6之间,P2O5与ΣREE具有明显的正相关关系,指示磷在沉积成矿过程中伴随着REE的富集。各类样品中(La/Sm)N比值介于0.50~2.64之间,(La/Yb)N比值为0.33~3.13,指示REE的富集以胶磷矿的吸附作用占主导。绝大多数岩/矿石具有"海水型"的REE配分模式,指示沉积成矿过程中的REE来自海水,且成岩阶段REE从海水向孔隙水转移过程中无明显的分馏;少量样品出现"帽型"REE模式,很可能是高水动力条件下胶磷矿发生破碎并短期暴露于海底,优先吸附MREE所致。所有样品明显的负Ce异常(Ce/Ce^*=0.31~0.88),指示沉积成矿过程中氧化-次氧化的底层水与孔隙水条件;部分样品出现不同程度的正Eu异常指示成矿过程中存在着海底热液的参与。The typical Tongchanggeng sedimentary phosphate deposit in Sichuan-Yunnan phosphorite belt occured in Lower Cambrian Maidiping Formation.Its depositional environment has been studied through analysis of REE geochemistry.The results showed that theΣREE of the tested samples ranged from 26.13×10^-6 to 172.42×10^-6,with a significant positive correlation between P2O5 andΣREE,indicating that phosphorus was enriched in REE during mineralization.The ratio of(La/Sm)N in various samples was between 0.50-2.64,and(La/Yb)N ratio is between 0.33-3.13,indicating that the enrichment of REE was dominated by the adsorption of collophosphate ore.The vast majority of rocks and ores had the REE distribution model of"seawater type",indicating that REE in the sedimentary and mineralization process came from seawater,and REE in diagenetic stage had no obvious fractionation in the process of transferring from seawater to pore water.The"hat-shaped"pattern of some reworked samples was possiblly caused by a preferential uptake of MREEs into the crystal lattice of phosphates during exposure to ocean water.Negative Ce anomalies in all samples(Ce/Ce*=0.31-0.88)suggested that they formed under oxic-suboxic bottom-water and pore-water conditions.Positive Eu anomalies in some samples were likely to reflect involvement of hydrothermal fluids.

关 键 词：稀土元素 磷矿床 沉积环境 铜厂埂 

分 类 号：P611[天文地球—矿床学] P595[天文地球—地质学]